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    <title>0420-01 rem</title>
    <style>
        html{
            /*1rem === 屏幕宽度 / 20 */
            /*font-size:16/62.5%px;*/
        }
        .box{
            font-size:1.2rem;
            border: 1rem solid #000;
        }
        span{
            display: none;
        }
        a:focus+span{
            display: block;
        }
        /*问题,没办法在位置右键来编译*/
    </style>
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<input type="file" name="user" id="">
<div class="box">熬枯受淡好艰苦</div>
<a href="#">啊卡时间花的卡技术的</a>
<span>熬枯受淡哈卡时间段哈看见</span>

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